This invention relates, in general, to transducers, and more particularly, to acceleration sensors.
Acceleration sensors such as yaw rate sensors are used to measure angular acceleration. A yaw rate sensor includes a proof mass suspended over a surface of a support substrate. The proof mass rotates around a z-axis in response to an acceleration force where the z-axis is perpendicular to the surface of the support substrate. The motion sensitivity of the proof mass around the z-axis is referred to as the theta-rotation sensitivity, which is a function of the theta-rotation spring constant. The proof mass also has a motion sensitivity along the z-axis, which is a function of the z-axis spring constant.
Yaw rate sensors should have a high z-axis spring constant and a low theta-rotation constant in order to reduce the motion sensitivity along the z-axis while maintaining a high theta-rotation sensitivity. One technique to increase the z-axis spring constant involves increasing the thickness of the support beams suspending the proof mass over the substrate while maintaining the width of the support beams. However, increasing the thickness of the suspension beams also undesirably increases the theta-rotation spring constant by a similar amount.
Accordingly, a need exists for an acceleration sensor having a low theta-rotation spring constant and a high z-axis spring constant.